Soil Properties, Growth, Mineral Content and Ultra-structural Leaf morphology of Swiss chard in response to landfill Leachates used as irrigation water

Abstract

Swiss chard cultivar was raised in greenhouse and irrigated with different concentrations of leachate obtained from the municipal landfill in Bellville, Cape Town, South Africa. The greenhouse experiment was laid out in a completely randomised design (CRD) replicated three times. Soil and crop samples were taken weekly after transplant and analysed to assess soil properties, growth and mineral contents of Swiss chard, post-irrigation. The leachate samples had a high electrical conductivity (mean = 383 mS cm-1 ) and high soluble salts content (mean values, Na: 714.5 mg/L, K: 56.8 mg/L, Ca: 133.7 mg/L, Mg: 68.8 mg/L, Cl: 983 mg/L); while the composition of heavy metals in the wastewater leachates were of low concentrations. The application of different concentrations of leachates as source of irrigation resulted in increased soil cation concentrations, particularly Na ions (increased sodicity). Similarly, an increase in electrical conductivity and pH were recorded in the soils after irrigation with leachates. The soil metal concentrations were low and there was no significant (p<0.05) difference in soil heavy metal concentrations between the soils irrigated with leachate and the controls. The result also shows significant (p<0.05) reduction (up to 50%) in Swiss chard growth (plant height) with application of all the three concentrations (100, 50 and 25%) of leachate as sources of irrigation water compared with the growth observed in leachate-free (control) irrigation systems. This reduction in growth was best attributed to the high cations content in plant tissue, picked up from the soil, which was high in these cations as a result of leachate irrigation. A study of the ultra-structural leaf morphology of the species using SEM revealed possible closure of the stomata opening induced by osmotic pressure, deposition of elements and reduced photosynthesis which would have limited carbon dioxide uptake and ultimately yield. The implication of this study on the possible agronomic improvement of Zn content in Swiss chard species tested is discussed. © 2017 Friends Science Publishers